The present invention relates broadly to seals and the like for the static or dynamic sealing of joints such as between the sections of an choke, kill, or other auxiliary line string which run along riser strings in offshore oil or gas drilling or production, or of other components, structures, or parts such as may be found in hydraulic or pneumatic cylinders or other actuators, and more particularly to a U-cup or solid geometry profile having a secondary sealing lip on both the inner and outer diameter thereof which functions as a wiper for the exclusion of outside contaminants, such as seawater, from the joint being sealed.
Fluid seals, also known as packing rings, for machine part joints are well-known in the art. A typical application therefor involves the provision of a fluid seal intermediate relatively movable or reciprocating surfaces such between as the outer surface of a rod or piston of a hydraulic or pneumatic cylinder, or other fluid actuator, and an internal bore or other inner surface of a stationary, surrounding housing, wherein the rod or piston reciprocates axially relative to the bore surface. Such seals, known in the vernacular as rod or piston seals as the case may be, conventionally are configured in a free state as a generally annular element which is molded or otherwise formed of an elastomeric or other resilient material such as a synthetic, natural, or co-polymer rubber, or a polymeric material such as a silicone, fluoropolymer, or, preferably, a polyurethane or fluoropolymer.
A more specialized application involves use as a static or joint seal such as between the tubular sections of a choke, kill, or other auxiliary line string of a oil or gas well drilling or recovery riser string which extends undersea between a rig or floating vessel and wellhead. Joints of such type are further described in International Publication Nos. WO 02/01038 and 02/36932, and in U.S. Pat. Nos. 6,367,554 and 5,992,893. As is known in the art, various fluids may be circulated through the lines and to the wellhead for various purposes.
Typically, the seal element is seated within an annular sealing gland or cavity which is provided within one of the surfaces, such as an internal bore of the cylinder housing or of a female end of a line section, with the opening of the gland oriented as facing the other surface such as the outer surface of the rod or the male end of a mating line section. Within the gland, the seal is interposed between the rod or male section end, which is received coaxially through the seal, and a circumferential, peripheral side wall of the gland. As the piston rod reciprocates along a longitudinal axis within the bore, or as the joint may be exposed to vibrational, torsion, flexing, or other forces, the seal functions to contact the reciprocating surface of the piston, or the circumferential section of the male end, and the side wall of the gland to provide dynamic and static sealing therebetween. In this regard, as installed under stress within the gland the seal typically presents in an energized or deformed state radial forward and rearward end faces, each disposed confronting a corresponding side of the fluid pressure system, and axial inner and outer diameter faces, each defining one or more contact surfaces with a corresponding, opposing surface of the rod or section and the gland. Of course, the described configurations may be reversed such that the gland is formed on the rod or the male section end.
Ideally, a seal element of the type herein involved should provide effective sealing under static and dynamic conditions, at both low and high pressure, and with a minimum of static and dynamic friction for a long, maintenance-free service life. However, particularly in the case of a rod seal, the seal must function not only to seal the against leakage, but also to wipe the rod of liquid or other fluid film which may adhere to the outer surface thereof as the rod is extended outward of the packing gland and cylinder housing. Similarly, as the rod is retracted, it is desirable again wipe the rod to remove any contaminants therefrom which could damage the packing or which could be carried past the packing and into the cylinder. To provide these noted sealing and wiping functions, it is customary to separate wiping and sealing members in a series arrangement with the wiper mounted a spaced-apart axial distance downstream of the seal. In general configuration, the wiper member may include an elongate wiper arm for a large surface area contact with the outer surface of the rod. The seal member, in turn, may be configured as a U-cup having a low pressure side heel portion and a high pressure side axial surface which is asymmetrically bifurcated by a radially-extending channel to define, in a stressed orientation of the seal, an inner sealing lip for dynamic contact with the outer surface of the rod, and an outer sealing lip for static contact with the peripheral surface of the gland. Representative rod, piston, and wiping elements are described in International Publication No. WO 92/15807, in European Patent No. EP 204,110, and in the following U.S. Pat. Nos.: 6,290,235; 6,209,882; 5,553,872; 5,482,296; 5,472,216; 5,431,415; 5,143,382; 5,104,131; 4,935,876; 4,893,823; 4,889,349, 4,850,602; 4,723,782; 4,687,212; 4,553,761; 4,449,718; 4,417,503; 4,337,956; 4,328,972; 4,268,045; 4,231,578; 4,174,846; 4,155,557; 3,942,806; 4,013,299; 3,921,991; 3,885,801; 3,790,179; 3,642,209; 3,342,500; 3,339,932; 3,169,776; 2,997,318; 2,979,350; 2,907,596; and 2,521,248. Commercial seals and wipers are manufactured by, for example, and are disclosed in the literature of, the following companies: Parker-Hannifin Corporation, Engineer Polymer Systems Division, Salt Lake City, Utah; Parker Hannifin GmbH, Prädifa Packing Division, Bietigheim-Bissingen, Fed. Rep. of Germany; Power-Seal Corporation; Freudenberg-NOK, Milan, Ohio; W. S. Shamban Co., Santa Monica, Calif.; Busak & Luyken GmbH & Co., Stuttgart, Fed, Rep. of Germany; Martin Merkel GmbH & Co. KG, Hamburg, Fed. Rep. of Germany; and Greene Tweed, Kulpsville, Pa.
The demands placed on seals and sealing systems continue to increase. It therefore is believed that further improvements in the design of such seals and systems would be well-received by various industries.